Cheapest priced copy (Commander Legends): $0.49 at Card Kingdom, near mint, their price list as of .
Magus of the Order 
Creature — Human Wizard · 3/3 · Rare · Commander Legends · #242
{G}, {T}, Sacrifice this creature and another green creature: Search your library for a green creature card, put it onto the battlefield, then shuffle.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
2 printings · $0.49 to $2.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander Legends | 242 | Rare | $0.49 | $0.49 |
| Commander Legends | 682 | Rare | $0.99 | $2.49 |
3 rulings from Wizards of the Coast
- 10 November 2020Once you declare you're activating the ability, players can't take any actions until you've finished doing so. Notably, opponents can't try to remove Magus of the Order or green creatures you control to stop you from activating the ability.
- 10 November 2020You can't sacrifice additional creatures to search for more green creatures.
- 10 November 2020If Magus of the Order becomes nongreen, you can still activate its ability by sacrificing it and a green creature.